Q. 515.0( 1 Vote )
If the focus of a parabola is (0, –3) and its directrix is y = 3, then its equation is
A. x2 = –12y
B. x2 = 12y
C. y2 = –12x
D. y2 = 12x
Answer :
As focus lies on y – axis,
Equation is x2 = 4ay or x2 = -4ay,
Focus has a –ve co = ordinate, so equation is x2 = -4ay,
Co – Ordinate of focus = (0, -a)
-a = -3
a = 3
As per the equation,
x2 = -4ay
x2 = -4 (3) y
x2 = -12y
Hence, the required equation is x2 = -12y.
Option (A) is the answer.
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